Superconductivity in group IV semiconductors is desired for hybrid devices combining both semiconducting and superconducting properties. Following boron-doped diamond and Si, superconductivity has been observed in gallium-doped Ge; however, the obtained specimen is in polycrystalline form [Phys. Rev. Lett. 102, 217003 (2009)10.1103/PhysRevLett.102.217003]. Here we present superconducting single-crystalline Ge hyperdoped with gallium or aluminum by ion implantation and rear-side flash lamp annealing. The maximum concentration of Al and Ga incorporated into substitutional positions in Ge is 8 times higher than the equilibrium solid solubility. This corresponds to a hole concentration above 1021cm-3. Using density functional theory in the local-density approximation and pseudopotential plane-wave approach, we show that the superconductivity in p-type Ge is phonon mediated. According to the ab initio calculations, the critical superconducting temperature for Al- and Ga-doped Ge is in the range of 0.45 K for 6.25at.% of dopant concentration, being in qualitative agreement with experimentally obtained values.
KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: Support by the Ion Beam Center (IBC) at HZDR and the funding of TEM Talos by the German Federal Ministry of Education of Research (BMBF) through Grant No. 03SF0451, in the framework of HEMCP, is gratefully acknowledged. We would like to thank Andrea Scholz for XRD measurements and Romy Aniol for TEM specimen preparation. This work was partially supported by the German Academic Exchange Service (DAAD, Project-ID:57216326) and National Science Center, Poland, under Grant No. 2016/23/B/ST7/03451. Partial support by the EU
7th Framework Program, Project No. REGPOT-CT-2013-316014 (“EAgLE”) and by the Foundation for Polish Science through the IRA Program cofinanced by the EU within SG OP is also acknowledged.